address comments

pkg/planner/core/recheck_cte.go

@@ -1,4 +1,4 @@
-// Copyright 2016 PingCAP, Inc.
+// Copyright 2023 PingCAP, Inc.
 //
 // Licensed under the Apache License, Version 2.0 (the "License");
 // you may not use this file except in compliance with the License.
@@ -14,24 +14,20 @@
 
 package core
 
-import "github.com/pingcap/tidb/pkg/util/intset"
-
 // RecheckCTE fills the IsOuterMostCTE field for CTEs.
 // It's a temp solution to before we fully use the Sequence to optimize the CTEs.
 // This func will find the dependent relation of each CTEs.
 func RecheckCTE(p LogicalPlan) {
-	checked := intset.NewFastIntSet()
 	ctes := make(map[int]*CTEClass)
 	inDegreeMap := make(map[int]int)
-	findCTEs(p, &checked, ctes, true, inDegreeMap)
+	findCTEs(p, ctes, true, inDegreeMap)
 	for id, cte := range ctes {
 		cte.isOuterMostCTE = inDegreeMap[id] == 0
 	}
 }
 
 func findCTEs(
 	p LogicalPlan,
-	checked *intset.FastIntSet,
 	ctes map[int]*CTEClass,
 	isRootTree bool,
 	inDegree map[int]int,
@@ -41,18 +37,17 @@ func findCTEs(
 		if !isRootTree {
 			inDegree[cte.IDForStorage]++
 		}
-		if checked.Has(cte.IDForStorage) {
+		if _, ok := ctes[cte.IDForStorage]; ok {
 			return
 		}
 		ctes[cte.IDForStorage] = cte
-		checked.Insert(cte.IDForStorage)
-		findCTEs(cte.seedPartLogicalPlan, checked, ctes, false, inDegree)
+		findCTEs(cte.seedPartLogicalPlan, ctes, false, inDegree)
 		if cte.recursivePartLogicalPlan != nil {
-			findCTEs(cte.recursivePartLogicalPlan, checked, ctes, false, inDegree)
+			findCTEs(cte.recursivePartLogicalPlan, ctes, false, inDegree)
 		}
 		return
 	}
 	for _, child := range p.Children() {
-		findCTEs(child, checked, ctes, isRootTree, inDegree)
+		findCTEs(child, ctes, isRootTree, inDegree)
 	}
 }